Catheter-type instrument



June 7, 1949. 1.. H. KRIPF'ENDORF 2,472,434

CATHETER-TYPE INSTRUMENT Original Filed May 5, 1944 Patented June 7, 1949 Original application May 55, T1944, FSeiia'l JNo.

534207, now Patent No. $337,542,

dated March 9, 1948. Divided and this application De'cemher 110, 1947, Serial ?N0. 790*;819

This application is a division :of smyaco-pending application, Serial No. 534,207, filed May 5, 19.44, 'nowiPatentiNo.23313542.

:The invention vrelates generally to surgical instruments :and has particular reference to oatheteratype'instruments.

By the term catheter-type instrument, :as used herein 'and in the appended claims, I intend :to refer to the well-known :kind of device which is inserted endwise into and through constricted body channels for diagnostic, therapeutic and allied purposes. illustrative of such instruments are :ureteral and :urethral catheters, bougies, fili- Torms-andthedike.

A -.conv.entional :instrument of this 'type :is of elongated :character and has a uniform over-tall flexibility coupled with sufficien't rigidity to permit its :endwise advancement. This paradoxical requirement for both flexibility and rigidity has heretofore presented a peculiar problem to :the manufacturer. For example, in the case of 2a ureteral catheter, it must be of suflicient flexibility to permit the tip of the instrument to advance harmlessly through thelconstrictediureteral canal and readily to *follow the curvatures s-encountered, yet as the flexibility is increased by the manufacturer to meet this requirement, the body portion loses-some of the rigidity necessary to enable the operator to eliect the desired advancement by endwise pressureexerted upon the rear end of the instrument' Similarly, in the case of -b'ougies or the like, it may under certain circumstances be desirable to increase "the rigidity of the :tip portion, yet the instrument .as a whole may thereby become-too inflexible toffiollow .anirregularlycurvedpath with adequate ease.

The principal :object of :my :present invention is directed toward a solutionof this'problem, and

'my invention is predicated upon the discovery that a catheter-type instrument may be caused to embody different flexibilities along its longitudinal :axis without materially altering its basic structural nature or impairing the other inherent qualities which .it necessarily must possess. This desirable and advantageous-result is achieved in an entirely practical and commercially-feasible manner.

.In accordance With one conventional manuiacturin'g procedure, the construction of a catheter-type instrument involves the formation inf an initially limp fabric base of intertwined threads, this base being usually first impregnated with aflflexible. stiffening medium and then coated with a flexible varnish. In the ,practice oixmy present invention, this general procedureiis 4 Claims. (Cl.l138.49)

adhered\to,ryet :the ;body portion of @the resultant instrument may be 'fcaused to embody a flexibilityi'in the forward or other section thereof which is :to :a predetermined (extent iappreciably greater or v:less than the rflexibility in an/adj acent section.

This new :result and its .corresponding advantageswmay be accomplished in the manner illustratively rexemplified imthe accompanying drawing;imwhich:

F.'igure \1 v is raiperspective view I of atypical catheter-Ltypednstrument;

Figure '2 is an enlarged fragmentary view "of a portion of the instrument with itheuouter coating ebroken away sto reveal the fabric base in the reglonlo'f the :line A- A -:.of :Figure 1; and

,Figure 3 isra diagrammatic view 'illustrating'the comparative charact'eri-stics, as :far as flexibility is concerned, of a conventional catheter-type instrument and one which has been constructed in accordance =withthe Zpresen't invention.

.The features of the invention may best be described -by Fbrief preliminary reference toconventicnah racti'ce.

A ifabnic :base :is :first created. Usually, this base ,assumes the form 10f an elongated hollow tube, but under certain circumstances it .need not have a :longitudinal apassageway extending through it. This :base is :formed of intertwined threads *of silk, cotton, 'or synthetic fibre, and usually \the threads are braided into the desired relationship. Any Weaving or other procedure maybe resortedrto, hQW'BVeIfiif desired, although braiding :machines have ;proven :to "be admirably suited to produce .a tubular i0! elongated fabric base-of the character required. Thisbase is initially limp in 1character,:arrd.=is customarily impregnated "with a flexible :stifiening medium of suitable composition Where the base isa-tube, the impregnation is carried out while the tube is mounted upon a suitable and or mandrel. After wiping on any excess, the mandrel (if one has been used) isiremoved and ithe impregnating :medium is =caused .to harden or cure, seither by-air drying, sor by ssubj action to a baking ;-procedure or the like. The reinforced and strengthened .fabric base is .then -.subiected ,to '-a series of operations during lwhichv a flexible tough varnish coating is applied -to it, layer bylayer, the successive coatings being cured :by baking of analogous procedures. After thedesired coating-hasrbeenformed, I

it is burnished and the instrument is subjected to such other finishing processes as may be deemedflesirable.

The forward tip of the instrument may be iorm'edleither pri'or to ,or after the initial impreg-l nation of the fabric base, depending upon the nature of the instrument, and the kind and shape of tip which it is intended to have. In the case of catheters, the several openings or eyes which characterize these instruments may be formed at or near the forward tip either during the braiding of the base or during a subsequent stage of treatment.

Depending upon the nature and size of the threads originally employed in forming the fabric base, upon the dimensions of this base and upon the impregnating and coating media which are employed, the resultant instrument will have a size and flexibility of predetermined character. Heretofore, in an instrument in which the body portion is of substantially uniform diameter, the bendability and over-all semi-rigidity has been uniform throughout, being usually determined by a suitable compromise between the flexibility required for any given purpose and the stiffness called for by the well-known method in which the instrument is to be employed.

In accordance with my invention, the essential nature of the manufacturing process remains unchanged, yet varying degrees of flexibility may be imparted to the resultant instrument along its longitudinal axis. For illustrative purposes, I have chosen to describe and illustrate the manner in which a catheter may be caused to have an appreciably increased flexibility in its forward region adjacent to the tip, as compared with the flexibility and rigidity of the remaining main portion thereof.

Thus, in Figure 1, I have illustrated a catheter II] in which the region forwardly of the dot-anddash line A has been caused to embody a greater flexibility than the remaining main portion of the catheter.

The procedure followed in accordance with the present invention is illustrated in Figure 2, which shows the structure in the vicinity of the dot-and-dash line AA. The initially limp fabric base tube is formed of two separate portions I 5 and I6 arranged in overlapping nested relationship. These portions may be formed of different materials or may be composed of threads of the same material but having different calibres. Or, if desired, both the material of the threads and their calibres may be different. In any case, the portion I5 is caused to embody an inherent structure which is suitably different from the portion l6 so that after impregnation and curing, these two portions will exhibit appreciably different fiexibilities.

Where the instrument has its forward portion more flexible, as indicated in Figure 1, the base tube section in the forward region is of such structure that it has greater flexibility than that of the other section.

The separate parts of the base tube may be brought into the overlapping relationship shown during the course of the braiding procedure. This composite base tube is then impregnated with a flexible stiffening medium which may be, for example, of the general type in which a suitable carrier such as tung oil is associated with a resin or resins of polymerizable type, together with a plasticizer or other customary ingredients. There are numerous resins which can be employed, and among them are, for example, resins of the phenolic type. The plasticizer used may be any of the usual ones, such as castor oil, dibutyl phthallate, tri-cresyl-phosphate, and the like.

In practice, the tube may be mounted on a suitable rod or mandrel (not shown) either before or after the forward tip is formed, and may then be dipped into the impregnating medium. The excess is then wiped off and the impregnated tube may be placed in a suitable oven to bring about a curing of the impregnating medium. At a suitable occasion the mandrel is withdrawn, and subsequently the tube is handled in the usual fashion to form on it the outer coating I4 of flexible varnish, which may be composed, for example, of a tung oil base, a phenolic or other suitable resin, and a plasticizer. This outer coating produces a tough flexible film having a smooth glossy surface and resistant to water, body fluids generally, and standard types of sterilization. The coating of flexible varnish serves to integrate the base tube portions to form a single and unitary body, and in the finished instrument it will be found that the exterior surface is entirely smooth and uniform despite the overlap in the interior, which is shown on an exaggerated scale in Figure 2.

Another way of imparting the desired difierences in flexibility to the portions l5 and I6 of the base tube, or of enhancing differences which are otherwise present, is to cause one of the portions l5 and I6 to be more loosely intertwined than the other.

The basic difference between the instrument of Figure 1 and the ordinary type of instrument is indicated diagrammatically in Figure 3. If the ordinar catheter I8 is pressed endwise against an abutment wall ill, by pressure exerted in the direction indicated by the arrow 29, it will buckle throughout its length. On the other hand, if the instrument ID of Figure 1 is similarly pressed against an abutment I9 by a similar pressure exerted along the direction of the arrow 2|, it will buckle in the forward region of greater flexibility, but not otherwise. Accordingly, when the instrument I0 is inserted into and advanced through one of the ureters or through any other similar constricted body canal, it will feel its way more easily past the curvatures encountered, and this makes the operation safer and simpler.

While I have illustrated a catheter, it will be understood that the invention is equally applicable to any catheter-type instrument, Whether hollow or not; and while I have chosen to illustrate the manner in which the forward region of the instrument may be made more flexible than the balance, it will be understood that other relative flexibilities may be produced, depending upon particular requirements.

In general it will be understood that the details herein described and illustrated to explain the general nature and objective of the invention may readily be modified by those skilled in the art Without departing from the spirit and scope of the invention as expressed in the appended claims.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

1. In an elongated flexible catheter-type instrument, a fabric base formed of intertwined threads, the threads in one region of said base being of the same material as, but of appreciably lesser calibre than, those in a longitudinallyacljacent region thereof, the flexibilities of the corresponding sections of the instrument being correspondingly affected.

2. In an elongated flexible catheter-type instrument, a fabric base tube comprising longitudinally-adjacent portions nested in overlapping relationship, each portion being separately formed of intertwined threads and having a flexibility diiferent from that of the other portion, and a coating of flexible varnish integrating said base tube portions to form a single body portion in which the flexibilities of the corresponding sections are correspondingly afiected.

3. In an elongated flexible catheter-type instrument, a fabric base tube comprising longitudinally-adjacent portions nested in overlapping relationship, said portions being separately formed of intertwined threads of the same material but of different calibres whereby one of said portions has a flexibility different from that of the other, and a, coating of flexible varnish integrating said base tube portions to form a single body portion in which the flexibilities of the corresponding sections are correspondingly affected.

4. In an elongated flexible catheter-type instrument, a fabric base tube comprising longitudinally-adjacent portions nested in overlapping 20 2,437,54

6 relationship, said portions being separately formed of intertwined threads, the threads in one of said portions being of different material from those in the other whereby one of said portions has a flexibility different from that of the other, and a coating of flexible varnish integrating said base tube portions to form a single body portion in which the fiexibilities of the corresponding sections are correspondingly affected.

LOUIS H. KRIPPENDORF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 757,877 Bosch Apr. 19, 1904 1,776,879 Baekeland Sept. 30, 1930 Krippendorf Mar. 9, 1948 

